package com.potato.study.leetcode.p0328;

import com.potato.study.leetcode.domain.ListNode;

/**
 * 
 * @author liuzhao11
 * 
 *         328. Odd Even Linked List
 * 
 *         Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.

You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.

Example 1:

Input: 1->2->3->4->5->NULL
Output: 1->3->5->2->4->NULL
Example 2:

Input: 2->1->3->5->6->4->7->NULL
Output: 2->3->6->7->1->5->4->NULL
Note:

The relative order inside both the even and odd groups should remain as it was in the input.
The first node is considered odd, the second node even and so on ...
 * 
 *         思路： 328. Odd Even Linked List

next 标志下一个node
num 当前node index
奇数头结点
偶数头结点
 * 
 */
public class Solution {

    public ListNode oddEvenList(ListNode head) {
        ListNode oddHead = new ListNode(-1);
        ListNode evenHead = new ListNode(-1);

        ListNode curOdd = oddHead;
        ListNode curEven = evenHead;

        ListNode p = head;

        int index = 1;

        while (p != null) {
            if (index % 2 == 1) {
                curOdd.next = p;
                curOdd = curOdd.next;
            } else {
                curEven.next = p;
                curEven = curEven.next;
            }
            p = p.next;
            index++;
        }
        curOdd.next = evenHead.next;
        curEven.next = null;
        return oddHead.next;
    }
	
	public static void main(String[] args) {
	}
}
